1. Field of the Invention
This invention relates to the field of analog to digital converters, and in particular, to an arrangement for extending the range of analog to digital (A/D) converters found in microprocessors and other integrated circuits.
2. Description of Related Art
Many microprocessor controller chips provide integral A/D converters to allow measurement of external circuit potentials. These integral A/D converters often have multiplexed inputs, so that readings from multiple sources can be acquired with a single software command. While economical, these on board A/D converters usually only provide 8 or 10 bits of resolution. If circuit demands either require higher resolution or an enhanced dynamic range, a much more costly external A/D converter must be provided.
External A/D converters can also have a similar structure, namely a plurality of input pins, which acquire their samples simultaneously, or if not simultaneously, within a very short time relative to the parameter being measured. For purposes of this application, the term simultaneously and the phrase within a very short time will be deemed to be encompassed by the phrase substantially simultaneously.